Well the appeal has finally been completed and it's got a couple of interesting points of case law in it. Especially points 16 and 64
http://www.bailii.org/ew/cases/EWCA/Civ/2007/1353.html
Not easy reading but might be relevant for some of you out there. Here the two bits that set some alarm bells ringing for me
16
# It must be kept in mind, first, that – in making the application for consent – the applicant must be taken to have accepted that it was not necessary to fell the tree in order to prevent or abate the nuisance. If it were necessary to fell the tree for the prevention or abatement of the nuisance the 1974 order would have no application: section 198(6)(b). There would be no need to seek consent under article 2 of the order. Second, that the application was for consent to fell the tree: there was no application (so far as appears from the statement of agreed facts or from the refusal notice) for consent to carry out works of topping or lopping: in particular, there was no application for consent to cut the encroaching roots. Third, that the factors which the local planning authority may take into account in deciding whether to grant or refuse consent under a tree preservation order are not the same as the factors which would lead to a decision that it was, or was not, necessary for the prevention or abatement of a nuisance to cut down, uproot, top or lop a tree in respect of which a tree preservation order had been made. Indeed, as I have pointed out, it is only in cases where it is not necessary to carry out the proposed operations to the tree in order to prevent or abate the nuisance that the question whether to grant or refuse consent to those operations can arise.
64
# If, as is obviously the case, the underlying purpose of the legislation is to preserve trees which are the subject of tree preservation orders, it would seem counterintuitive to that purpose, when considering what is the minimum necessary that needs to be done in order to prevent or abate a nuisance caused by a tree that is the subject of a tree preservation order, to ignore altogether steps that may be taken other than to the tree itself and, instead, focus simply on works to the tree, albeit that the works to the tree are to be the minimum necessary. Take the case of an overhanging branch which, if it falls, will damage a structure on the neighbour's land. Why should the legislation permit the lopping of the branch which, let it be assumed, is the minimum work to the tree (in the way of cutting down, uprooting, topping or lopping) to prevent or abate the nuisance when, by the use of, for example, a prop which will cause no damage to the tree, the imminent danger can be avoided? Why should it be permissible to dig down to cut an encroaching root which threatens to damage buildings foundations on the neighbour's land but impermissible to consider, having dug down to the roots, the insertion of a barrier which would be as effective?